Adds SGN.md page

CHANGELOG.md

@@ -1,4 +1,4 @@
-[v1.18.0](https://github.com/boriel-basic/zxbasic/tree/v1.18.1)
+[v1.18.1](https://github.com/boriel-basic/zxbasic/tree/v1.18.1)
 ===
 + ! Fixes crash on simple cast from i32 to u32 and vice versa
 

docs/overrides/stylesheets/extra.css

@@ -34,7 +34,7 @@
 }
 
 /* Responsive adjustments for smaller screens */
-@media screen and (max-width: 768px) {
+@media screen and (max-width: 1220px) {
   [data-md-color-scheme="default"] .md-header {
     height: 3.5rem;
   }
@@ -107,7 +107,7 @@
   }
 
   .md-header__button {
-    margin: 0;
+    margin: 2px;
     padding: 2px;
   }
 

docs/sgn.md

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+# SGN
+
+## Syntax
+```basic
+SGN(expression)
+```
+
+## Description
+
+Returns the sign of a numeric expression as follows:
+* -1 if the number is negative
+* 0 if the number is zero
+* 1 if the number is positive
+
+The returned value type is [byte](types.md#Byte).
+
+## Examples
+
+```basic
+REM Print sign of different numbers
+PRINT "Sign of -5 is "; SGN(-5) ' Prints -1
+PRINT "Sign of 0 is "; SGN(0) ' Prints 0
+PRINT "Sign of 3.14 is "; SGN(3.14) ' Prints 1
+```
+
+## Remarks
+
+* This function is 100% Sinclair BASIC Compatible
+* If the argument is an unsigned value, the result will always be either 0 or 1
+* Using SGN with string expressions will result in a compile-time error
+
+## See also
+
+* [ABS](abs.md)